1. Technical Field
Various embodiments of the present disclosure relate to an apparatus and method for controlling steering return of a motor driven power steering system, and more particularly, to an apparatus and method for controlling steering return of a motor driven power steering system, which enables an overshoot-free center stop to be made as well as enables a quick return to be made, when returning after steering by a large steering angle in the motor driven power steering system.
2. Related Art
In general, a motor driven power steering system (MDPS) enables a handling to be light by providing an auxiliary torque in a driver's steering direction using an electrical motor.
The motor driven power steering system automatically controls an operation of the electrical motor according to a driving condition of a vehicle to improve a steering performance and a sense of steering, unlike the conventional hydraulic power steering system (HPS). At this time, the motor driven power steering system includes a torque sensor for measuring a driver's steering torque inputted to a steering wheel, a steering angle sensor for measuring a steering angle of the steering wheel, and a vehicle speed sensor for measuring a vehicle speed, and determines a driving condition of the vehicle.
Meanwhile, when the driver turns the vehicle after adding a steering input, if the driver determines that the turns of the vehicle are done to some extent, the driver slowly releasing the hands from the steering wheel, but the steering wheel returns to the center by a returning act.
The returning act of the steering wheel is generated by a self-alignment torque of tires of the vehicle, and generally, is useful function when the vehicle turns in a speed of 5 km/h˜30 km/h.
However, the self-alignment torque given to the steering wheel becomes not sufficient to return the steering wheel to the center, as a residual steering angle is remained due to an act of a frictional force of the system. Thus, in order to fully return the steering wheel to the center, a function to assist the returning act should be separately given.
Accordingly, the motor driven power steering system applies a returning torque that is calculated on the basis of the steering angle to assist the returning act of the steering wheel and to improve the returning performance.
In the motor driven power steering system, when providing the returning force and a damping force to the steering wheel, the damping force is a function for a vehicle speed, and calculated on the basis of a column torque and column speed.
However, when returning the steering wheel, if the damping force is controlled to have an excellent returning performance, an overshoot occurs at a center portion of the steering wheel, and if the damping force is controlled to reduce the occurrence of the overshoot, a returning speed is reduced.
The related art of the present disclosure is disclosed in Korean Patent Registration No. 10-0247334 registered on Dec. 10, 1999 and entitled “Electric power-assisted steering”.